Preparation And Evaluation Of Insulin-loaded PLGA Nanospheres By Oral Administration

In recent years,protein and peptide drugs are used to treat various human diseases due to their low toxicity,few side effects,high efficacy and good pertinence.They could be inactivated in the gastrointestinal tract,presently,the majority of protein and peptide are administrated by injection,resulting in reduced patient compliance.Drug administration via the oral route is simple,non-invasive,painless,and thus often associated with improved patient compliance.A number of strategies have been investigated so far in order to overcome multiple barriers.However,due to the physical and chemical properties of protein and peptide drugs,low oral bioavailability is still a bottleneck for clinic application of oral fromulations.In this study,insulin is chosen as a model drug and biodegradable material PLGA as carrier material,and insulin-loaded PLGA nanospheres with different particle size for oral administration are prepared by ultrasonic emulsification technology combined with solvent evaporation method.The surface of nanospheres was modified by cys-MNA and CSK peptide.The modifications of cys-MNA make nanospheres penetrate mucus and increase the contact with intestinal epithelial cells;CSK peptide was identified to have good affinity with the goblet cell,which could prominently improve the transport efficiency of macromolecules across the intestinal mucosal barrier.Therefore,the constructed peptide delivery system may exhibit promising potential for increasing oral bioavailability.The detailed research contents are as follows:(1)The insulin-loaded PLGA nanospheres were successfully obtained by optimizing parameters employing the particle size and encapsulation efficiency as evaluating indicator.The insulin-loaded PLGA nanospheres obtained under optimal parameters showed particle diameter with 100 nm and 300 nm,and the insulin encapsulation efficiency 48.73%±0.51%and 62.15%±0.29%,respectively.These nanospheres were uniform particle size and regular spherical appearance,and they showed slow drug release profile in vitro.Compared with the native insulin samples,insulin released from the PLGA nanospheres maintained the secondary structure and the tertiary structure of proteins.(2)The cellular and animal effects of insulin-loaded PLGA nanospheres with different particle sizes were evaluated.These nanospheres had nontoxic effect.It was found that PLGA nanospheres with size of 100 nm exhibited a better intestinal absorption,cumulative hypoglycemic effect,relative biological availability after oral administration compared with those of PLGA nanospheres with size of 300 nm.(3)In order to improve the oral bioavailability of drug,the PLGA nanospheres with size of 100 nm were modified with cys-MNA and CSK peptide.The results exhibited the modifications of cys-MNA have greatly improved mucoadhesive properties,and CSK peptide could prominently improve the transport efficiency of nanospheres across the intestinal mucosal barrier,which further demonstrated more prolonged hypoglycemic activity in vivo.In summary,the nanospheres developed in this study are a promising delivery system for oral protein or peptide delivery.